1.題意

104. Maximum Depth of Binary Tree

Easy

98540

Given a binary tree, find its maximum depth.

The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.

Note: A leaf is a node with no children.

Example:

Given binary tree [3,9,20,null,null,15,7]

    3
   / \
  9  20
    /  \
   15   7

return its depth = 3.

2.程式碼

class Solution {
public:
    int maxDepth(TreeNode* root) {
        if(root==NULL) {
            return 0;
        }
        else 
            return max(1 + maxDepth(root -> left), 1 + maxDepth(root -> right));
    }
};